Cengiz Metin

The effects of different cod-end design on bottom trawl selectivity in Turkish fisheries of the Aegean Sea

Abstract The effect of different cod-end designs on bottom trawl selectivity was studied using the hooped cod-end cover method. The selectivities of three different cod-ends: standard, 15% shortened lastridge rope and narrowed circumference (to 120 mesh from 150 mesh), were measured for red mullet ( Mullus barbatus L., 1758) and annular sea bream ( Diplodus annularis L., 1758) in Turkish territorial waters of the Aegean Sea in June and September 1994. Selection curves and selection parameters were calculated using a logistic model. 50% retention lengths and selection factors for red mullet were higher for the shortened lastridge rope case and narrow cod-end than the standard cod-end. There was no significant difference for annular sea bream. This can be explained by the body shape differences of the two species. The effects of different cod-end designs on the selectivity are discussed.

A new artificial reef design for octopus (Octopus vulgaris cuvier, 1797) in the Aegean sea and preliminary results

This study was carried out in the Gulf of 0zmir in the Aegean Sea between June 2006 and November 2008. The purpose was the creation of a new concept of the artificial reef for Octopus vulgaris, with a view to establishing new artificial reef sites to be used in the fisheries management of this species (MPA, NTZ or fishing areas). First, the main characteristics of natural octopus nests were recorded (entrance width, length, etc.) by divers. These characteristics were used in the construction of new octahedral artificial reef blocks. The blocks were made of reinforced concrete, in a shape like that of an inverted pyramid, with an upper surface of 100x100x25 cm3 and a lower one of 60x60 cm2. Four cylindrical holes each with two ellipsoidal openings were placed in one face and in the lateral edge of the octo-block, to serve as the entrances to the artificial nest. Each nest has a volume of 5000 cm3. Eighty octo-blocks were deployed as artificial reefs at 10 m from each other at 15 different depths at two sites by divers with the help of the winch of the R/V EGESUF. These artificial octo-reefs were censused by direct observation. Twenty-eight octopuses were sampled at the end of 25 dives. Minimum mantle length of the octopuses was 75 mm and the maximum 249 mm, with an average of 152.71 mm. The average total length was calculated to be 918.57 mm. The weight of the specimens was between 244 g and 7140 g with an average of 2335.43 g. The results showed that both sites were inhabited by octopuses coming from the artificial reefs, which used them as nests. These nests seem to have constituted special places for fisheries management and will permit the assessment of reserve areas or marine protection areas (MPA), thus opening up a new perspective for Turkish fisheries.

Determination of the Tissue Distribution of PPO on Caramote Prawn (Melicertus kerathurus, Forskal, 1755) and Jinga Shrimp (Metapenaeus affinis, H. Milne Edwards, 1837) Caught from Izmir

Tissue distribution of polyphenol oxidase (PPO) was studied in caramote prawn (Melicertus kerathurus) and jinga shrimp (Metapenaeus affinis) postmortem. Activity was analyzed in different tissues: the head (cephalothorax + carapace), carapace, exoskeleton of the abdomen, pereopods, and maxillipeds, individually. Based on the results, PPO activity of jinga shrimp was determined to be higher than caramote prawn during the research period. Partial tissue distribution showed that the highest activity was determined in carapace by using 70% ammonium sulfate fractions. Partial tissue distribution was also used to determine the spread of black spots. In addition, comparison between the PPO levels of caramote prawn and jinga shrimp was performed. The importance of these species is their economic value. However, there is no available data in the literature about caramote prawn and jinga shrimp. The determined data showed us that using antioxidant chemicals would be suitable for jinga shrimp.